This invention relates to the manufacture of tubular fittings and, more specifically, to a novel method of forming high quality elbow and return bend fittings from straight tubular lengths.
Numerous methods of forming elbow and return bend fittings have been developed over the years. U.S. Pat. No. 3,354,681 discloses a method and apparatus for forming elbows from a tubular section by pushing through a forming die. A portion of this apparatus consists of a "tapered land" which the inventor claims to cause bending by differential friction, the friction force being greater on the inside radius of the bent tubular section than on the outside radius, which is in direct contradiction to the finding of our invention.